May is traditionally a month many of us trade the skis for hiking boots. At low elevations, trails have been dry and clear of snow for months. But at high elevations, this snow often lasts into July or even August. This isn't just because of colder temperatures.
To illustrate this, let's take a look at Quandary Peak. It's currently the second busiest 14er in Colorado according to data from the Colorado 14ers Initiative (CFI).
Snow covers the entire standard route from its base at around 11 thousand feet to its summit at 14,272 feet. In most spots, it's several feet thick.
Off the bat - yes - it is much colder at these elevations than along I-25. For every 1,000 feet of elevation gain, average temperatures decrease by 3-4 degrees Farenheit. So - if the average temperature (in a 24 hour span) in Colorado Springs is 60 degrees, the average temperature at 14,000 feet is 32. While there is daily variation in average temperature and in the rate of temperature decline with height this rule works well over the span of a full year. In May and June this means that the average temperature at high elevations tends to still be near freezing.
But if that were the only reason, we'd still see most snow melt out in June. Many 14ers hold snow into July, and some couloirs and gullys can hold snow into August. Air temperature alone won't explain that.
Quandary Peak's standard route traces the east ridge of the mountain. On most of the plains, direct sunlight hits the ground for most of the day. On 14ers, the giant change in elevation means you cut that time by a third or more on any given slope.
The mountain blocks the sun from hitting westerly slopes in the morning and easterly slopes in the afternoon. Less sunlight means less energy to melt snow.
Next - the ground is also typically frozen. Above around 12 thousand feet in Colorado it is actually frozen year-round according to research from the Metropolitan University of Denver. The technical term for this is permafrost. So, as snow melts and trickles down to the frozen ground, it can often refreeze.
Finally, the sheer amount of snow plays a role. The vast majority of Colorado's precipitation falls within the mountains. Snowstorms can continue into June on the 14ers, providing fresh snow and compacting older snow.
The upshot here is that cold air is not the only reason our high mountain summits keep snow into the summer. South-facing slopes get the most sunlight, so they tend to melt fastest—something to keep in mind as you plan your spring hikes.
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